1. Field of the Invention
The present invention is directed to a method for the electrophotographic printing of a print image having a plurality of colors on a carrier, whereby the print image contains at least first image element with the color of the carrier, at least one second image element with a second color and at least one third image element with a third color. The first image element is allocated to a first surface element of a photo conductor layer. The photo conductor layer and an electrode layer carrying a predetermined reference potential are contained in a light-sensitive layer system. The reference potential is usually the zero potential. The second image element is allocated to a second surface element and the third image element is allocated to a third surface element of the photo conductor layer.
2. Description of the Related Art
A method for color printing is disclosed, for example, by U.S. Pat. No. 4,078,929. The method disclosed therein bears the name "Tri-Level Method". What is disadvantageous in this method is that only toner particles of two colors can be applied in a printing process. Moreover, the developer stations for applying the toner particles are operated with electrical polarities that are opposite one another. This requires additional structural measures at the developer stations, so that the developer stations are not identically constructed. The individual developer stations or, respectively, their component parts as well as the toners as well are thus not interchangeable, and the manufacturing outlay and servicing outlay is higher than given identical developer stations and identical toners.
Japanese Patent Application JP-63265255 discloses a printing method wherein toner particles of only one polarity are employed for the application of three colors. Before developing the second and the third color, the potential of the surfaces of the photoconductor that are not yet covered is respectively lowered by a total illumination. At the same time, the potential of the most recently developed surfaces is boosted.
U.S. Pat. No. 5,155,541 discloses a method wherein techniques of color photography and of the tri-level method are combined. A lowering of the potential by a total illumination with a lamp ensues between two developing steps with the same toner polarity.
German Published Application DE 44 08 978 A1 discloses methods for image generation wherein a total illumination and, potentially, an increase of the potential as well is implemented between developing steps with the same toner polarity. Various methods are explained wherein the total illumination is implemented either before or after the boosting of the potential.
Japanese Patent Application JP 08 044140 A discloses a printing method for a multi-color printing wherein a total illumination is implemented between two developing steps in order to lower the potential on areas of the photoconductor that have not yet been developed.